Figure 1.
Selection of the superior longitudinal fasciculus (SLF).
The SLF was selected using a multiple region of interest (ROI) approach. Two “AND” ROIs (shown in yellow) were placed on a coronal slice and one on a sagittal slice. Reconstruction was based on a standardized atlas of white matter tracts [28].
Figure 2.
Selection of the medial segment of the corpus callosum (CC).
The CC was selected using a multiple region of interest (ROI) approach. The median ROI was placed on the midsaggital plane in MNI space, and the two segment-selecting ROIs were drawn two voxels (4 mm) to either side of the midsagittal plane.
Figure 3.
Fiber orientation distribution profiles estimated with the CSD method.
a) two crossing fiber populations in voxels in the superior longitudinal fasciculus. b) one fiber population in the corpus callosum.
Figure 4.
Crossing fiber regions in the superior longitudinal fasciculus (SLF).
Sub-regions of the SLF marked on a directionally encoded color map (top row) and planar diffusion coefficient encoded (Cp) map (bottom row). The planar diffusion coefficient ranges from zero to one and is relatively high in voxels were the tensor has a disc-like shape, which is typically the case when two fiber populations “cross”. The white line marks a sub- region of the SLF containing voxels with relatively few “crossing fibers”, which is reflected by a Cp close to zero. By contrast, the more anterior sub-region of the SLF, marked in yellow, contains relatively many voxels with “crossing fibers”, due to crossing with the cortico-spinal tract and/or laterally projecting fibers of the corpus callosum. This is reflected by a Cp closer to one.
Figure 5.
Crossing fiber regions reflected by the planar diffusion coefficient.
The superior longitudinal fasciculus (SLF) and medial segment of the corpus callosum (CC) color coded according to the value of the planar diffusion coefficient (Cp) (for interpretation of the color coding see also fig. 3). The figure shows regions with “crossing fibers” reflected by a Cp close to one (green) and regions with relatively few “crossing fibers” reflected by a Cp close to zero (red). a) the SLF shows many regions with “crossing fibers” due to crossing with the cortico-spinal tract and/or laterally projecting fibers of the corpus callosum (CC) in frontal regions, and with the inferior longitudinal fasciculus in temporal regions. b) In the midsagittal segment of the CC one fiber population predominates.
Figure 6.
Segmentation of the superior longitudinal fasciculus (SLF) with DTI and CSD based fiber tractography.
Segmentation of the SLF in four patients reconstructed with DTI (yellow) and CSD (red) based fiber tractography (FT). Delineation of the SLF resulted in larger and longer pathways with CSD compared to DTI based FT. With the DTI method, fibers of the SLF were more likely to terminate at crossings between the SLF and the cortico-spinal tract in frontal regions and between the SLF and the inferior longitudinal fasciculus in temporal regions.
Table 1.
Association diffusion parameters of the SLF and memory performance.
Table 2.
Tabel 2. Association diffusion parameters of the CC and memory performance.